As of 11:20 a.m. ET, the tally of flight cancellations today has topped 600, according to flight-tracking service FlightAware. Not all of those can be directly attributed to the storm, though that total comes largely from airports that have felt the storm's effects during the past 48 hours.

The scope of the cancellations is widening, now affecting airports from New York to Georgia to Texas. Among the other airports with a notable tally of cancellations today are: Washington Dulles (47); Cleveland (45); New York LaGuardia (45); Columbus (38); Charlotte (33); Cincinnati/Northern Kentucky (29); Washington National (29); New York JFK (28); Philadelphia (27); Newark Liberty (26); Dayton (25); Pittsburgh (23); Akron-Canton (20) and Atlanta (20).

Delays also are cropping up at major airports in the same regions. As of 11:35 a.m. ET, the Federal Aviation Administration's flight delay map shows delays averaging anywhere from 15 minutes to close to 90 at airports in Philadelphia (wind), Newark (wind) and Baltimore (congestion). Other problem spots on the FAA map are Dallas/Fort Worth and Fort Lauderdale. FlightStat's delay map shows an even more ominous picture, indicating significant delays at dozens of major airports in Midwest and along the East Coast.

Today's cancellations come on top of the more than 530 flights that were reported on the typically slow Christmas travel day. Most of those cancellations came at Dallas/Fort Worth, where yesterday's disruptions have spilled over into today's operations.

Also, as is now a common occurrence during major weather events, most big airlines have enacted flexible rebooking policies for customers scheduled to fly to or through the storm's path.

Blizzard warnings covered areas surrounding the Cleveland and Indianapolis airports, while windy wintry weather put a number of others at a significant risk of delay. Among those: Detroit, Cincinnati, Columbus, Pittsburgh and Buffalo.

Flight schedules at Cleveland's Hopkins International Airport likely will take a hit this afternoon.

The Plain Dealer reports: "United Airlines plans to cancel about 60% of its flights beginning at noon Wednesday because of the anticipated effects of the storm, said Cleveland Hopkins International Airport spokesman Todd Payne. United accounts for about 65% of all flights in and out of Hopkins airport, Payne said."

In Indianapolis, about a half of the airport's 300 combined arrivals and departures have been canceled for today, according to The Indianapolis Star. That number could grow as a blizzard warning remains in effect there through 7 p.m. local time. The Star writes "just one runway is being kept open for the few flights the airline companies are allowing to come in and out."

Elsewhere in the region, flight-monitoring service FlightStats shows significant delays as of 9:20 a.m. ET at several Midwest airports, including Cincinnati/Northern Kentucky, Columbus, Louisville, Indianapolis and Dayton.

Chicago O'Hare will not take a direct hit from this storm, but flights there could see sporadic delays because of windy conditions - and because of disruptions to Chicago-bound flights at other airports.

The storm also is expected to affect airports all along the East Coast. Wintry precipitation and poor visibility are forecast for the already delay-prone airports in Philadelphia and the New York City area. Strong winds could also create sporadic delays at other big airports in the East - including the world's busiest airport in Atlanta.

The three big airports in the Washington/Baltimore region have suffered nearly 100 cancellations combined, according to FlightAware. Sporadic delays from congestion and de-icing had been reported off-and-on this morning. And, of course, problems at other airports that affect Washington-bound flights could create problems for flight schedules at the three D.C.-area airports.

By this evening, the effects of the storm - notably strong winds - will extend into New England, adding Boston, Hartford and Providence to the list of airports where fliers could run into weather-related problems.